Refining of copper base alloys



p 1945- A. J. MURPHY ET AL 2,384,256

REFINING OF COPPER BASE ALLOYS Filed June 17, 1945 Patented Sept. 4, -1945 Alfred John Murphy, Petts Wood, and Geoffrey Thomas Callis, Pinner, England, assignors to .i. Stone & Company Limited, Deptford, England, a British joint-stock company Application June 17, 1943, Serial No. 491,196 In Great Britain May 26, 1942 1. Claim.

This invention comprises improvements relating to the refining of copper base alloys and is particularly concerned with such alloys when they result from the melting down of scrap metal, such as disused parts, trimmings, turnings and the like. It is often found that the alloys in question contain proportions of zinc and lead which are too great to permit of the immediate use of the alloys for purposes wherein the content of zinc or lead, or both, is required to be low.

The principal object'of the present invention is to enable copper base alloys to be refined by the aid of a tin compound, tin being a desirable component in many copper base alloys and therefore a very advantageous medium'for use in the displacement of such components as zinc lead or 11011.

According to this invention the vapours of stannous chloride are introduced beneath the surface of a molten mass of copper base alloy, whereupon a reaction occurs between the said vapors and the metal component to be displaced, the

said metal being transformed into a chloride which is separable from the mass and tin being incorporated into the alloy in place of such metal. Thus, in the event of a copper base alloy being found to contain too high a. proportion of zinc,

the reaction can be pre-determined to secure a given reduction of the zinc contentjzinc chloride being evolved during the reaction and tin at the same time being introduced intothe alloy.

If an alloy-contains lead but no zinc, the treatment aforesaid results in a decrease of the lead content and in an increase of the tin content. If both lead and zinc'are present, the reaction proceeds first principally with the zinc and the lead content is not greatly affected until the zinc has been largely removed.

The invention advantageously makes use of stannous chloride SnClz, which can be vaporized by heating at about 620 C. Stannous chloride is a solid crystalline material readily transported and handled by the means which are familiar to operatives in foundries and melting shops. The vapour may be generated from the stannous chloride by any one of a variety of methods.

According to one method of carrying out the invention, which may be described by way of example and with reference to the drawing, the desired quantity of stannou-s chloride 11 in the form of fused anhydrous salt is charged into atube b of refractory material which isopen at one end and closed at the other. The open mouth of this tube is loosely plugged with asbestos woolc sumciently compact to prevent the passage of solid or liquid stannous chloride but sufiiciently porous to permit vapour to pass. The charged tube is inverted with the plugged open end downwards, which end is then lowered beneath the surface of a molten mass of copper base alloy to be treated in a crucible a, the closed end of the tube remaining above the surface, as shown. Means for suspending the tube b is indicated diagrammatically by the line e. The stannous chloride is first melted and then vapourized by the heat of the molten metal, whereupon bubbles of stannous chloride vapour pass into the copper base alloy. The rate of passage of the chloride vapour can be controlled or varied by moving the tube upwards or downwards so as to vary the intensity of the heating. A charge of stannous chloride can be calculated for the displacement of a predetermined proportion of the zinc content for example, in a given weight of copper base alloy. When discharge of vapour ceases and the reaction is at an end, it is known that the zinc content has been reduced approximately to the extent desired and has been replaced by anamount of tin corresponding with the weight of stannous chloride employed for the charge. 1

The results achieved by the invention may be illustrated by the following tests:

(a) A gun metal containing copper, tin, zinc and lead was found by analysis to contain too high a proportion of zinc, to suit a, given specification. Accordingly it was treated in the manner hereinbefore described with the vapour of stannous chloride and a reduction-in the proportion of zinc was achieved to the extent shown by the'follow-" The tin content was thus increased by 36 per cent and the zinc content was simultaneously reduced by 46 per cent. The change in the lead content was smallas it was only reduced by about 5 per cent.

(b) A leaded tin bronze free from zinc was found to contain too high a proportion of lead.

A sample of this alloy was treated with sta-nnous' chloride, the amount of the latter being 2.2 per cent of the weight of the alloy, and a reduction in the proportion of lead was achieved to the extent shown by the following table:

Metal before Metal after treatment treatment Percent Percent 4. 77 o. Lead i 5. 09 3. 96 Copper and impurities Remainder. Thus, the lead content was reduced by 22.2

per cent and the tin content was increased by 34.6

per cent.

The particulars of yield given above demonl5 strate the high eificiency of the process in accordance with the present invention, in which process the whole of the tin available in the form of stannous chloride is recovered as alloyed tin in the final product.

From the foregoing, it is apparent that tin produced in the form of stannous chloride, as

of the said open end.

ALFRED for example in commercial processes recovering tin from scrap tin plate, can be employed for enriching the tin content of bronzes directly 4 and without the intermediate production of metallic tin.

The process in accordance with the presen invention oflers the two-fold advantage of an economical recovery of tin in the alloyed form and an effective means of reducing the proportions 01' zinc lead and iron in copper base alloys.

We claim: Refinement of a copper base alloy comprising the submergence in a molten mass of such alloy of a refractory container open at one end and holding a charge of stannous chloride, the-said open end being fitted with a porous closure and presented downwardly within the molten mass and the rate of generation of chloride vapour being controlled by varying the depth of submergence JOHN MURPHY. GEOFFREY THOMAS CALLIS. 

